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/*
* Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables_core.h>
#include <linux/jhash.h>
struct nft_hash {
enum nft_registers sreg:8;
enum nft_registers dreg:8;
u8 len;
u32 modulus;
u32 seed;
u32 offset;
};
static void nft_hash_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct nft_hash *priv = nft_expr_priv(expr);
const void *data = ®s->data[priv->sreg];
u32 h;
h = reciprocal_scale(jhash(data, priv->len, priv->seed), priv->modulus);
regs->data[priv->dreg] = h + priv->offset;
}
static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
[NFTA_HASH_SREG] = { .type = NLA_U32 },
[NFTA_HASH_DREG] = { .type = NLA_U32 },
[NFTA_HASH_LEN] = { .type = NLA_U32 },
[NFTA_HASH_MODULUS] = { .type = NLA_U32 },
[NFTA_HASH_SEED] = { .type = NLA_U32 },
[NFTA_HASH_OFFSET] = { .type = NLA_U32 },
};
static int nft_hash_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
{
struct nft_hash *priv = nft_expr_priv(expr);
u32 len;
int err;
if (!tb[NFTA_HASH_SREG] ||
!tb[NFTA_HASH_DREG] ||
!tb[NFTA_HASH_LEN] ||
!tb[NFTA_HASH_MODULUS])
return -EINVAL;
if (tb[NFTA_HASH_OFFSET])
priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
err = nft_parse_u32_check(tb[NFTA_HASH_LEN], U8_MAX, &len);
if (err < 0)
return err;
if (len == 0)
return -ERANGE;
priv->len = len;
priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
if (priv->modulus <= 1)
return -ERANGE;
if (priv->offset + priv->modulus - 1 < priv->offset)
return -EOVERFLOW;
if (tb[NFTA_HASH_SEED])
priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
else
get_random_bytes(&priv->seed, sizeof(priv->seed));
return nft_validate_register_load(priv->sreg, len) &&
nft_validate_register_store(ctx, priv->dreg, NULL,
NFT_DATA_VALUE, sizeof(u32));
}
static int nft_hash_dump(struct sk_buff *skb,
const struct nft_expr *expr)
{
const struct nft_hash *priv = nft_expr_priv(expr);
if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
goto nla_put_failure;
if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_LEN, htonl(priv->len)))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed)))
goto nla_put_failure;
if (priv->offset != 0)
if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
goto nla_put_failure;
return 0;
nla_put_failure:
return -1;
}
static struct nft_expr_type nft_hash_type;
static const struct nft_expr_ops nft_hash_ops = {
.type = &nft_hash_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_hash)),
.eval = nft_hash_eval,
.init = nft_hash_init,
.dump = nft_hash_dump,
};
static struct nft_expr_type nft_hash_type __read_mostly = {
.name = "hash",
.ops = &nft_hash_ops,
.policy = nft_hash_policy,
.maxattr = NFTA_HASH_MAX,
.owner = THIS_MODULE,
};
static int __init nft_hash_module_init(void)
{
return nft_register_expr(&nft_hash_type);
}
static void __exit nft_hash_module_exit(void)
{
nft_unregister_expr(&nft_hash_type);
}
module_init(nft_hash_module_init);
module_exit(nft_hash_module_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
MODULE_ALIAS_NFT_EXPR("hash");
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